Leather-like material and process of producing same



Patented June 21, 1938 LEATHER-11KB MATERIAL AND PROCESS OF PRODUCINGSAME John J. Moriarty, Toronto, Ontario, Canada, asslgnor to E. I. duPont de Nemours & Company, Wilmington, Del., a corporation of DelawareNo Drawing.

Application March 12, 1938,

Serial No. 68,574

1.01am (CI. 9188) This invention relates to leather-like material andprocess of making the same. More particularly, it relates to theproduction of a leatherlike material which can be made by treating a 5fabric base with compositions of rubber or rubber-like materials in sucha manner that a material having the appearance, stiffness and othercharacteristics of leather is produced.

Various processes have been devised for the manufacture of artificialleather in which a woven or unwoven fabric is impregnated or coated witha cementitious or adhesive material. The use of cements for this purposerequires special and costly methods of treatment for the impregnationand compacting of the fibrous material in order to obtain the necessarytensile strength and stiffness in the finished product. It was alsofound to be costly to impart a leatherlike appearance to the materialwhen the prior art methods were used. Liquid rubber latex was also usedto impregnate woven and unwoven materials, such as cotton felt. This wasnot entirely satisfactory because it caused excessive shrinkage of thefelt and consequent difiiculties in handling the material on themachines. Therefore, it is desirable to provide for improved, lesscostly and more convenient methods of production, and for avoiding thedescribed defects and other difliculties.

One of the objects of the invention is therefore the production of alatex-containing leather-like material.

Another object of the invention is the produc- 5 tion of a leather-likematerial having the ap- 3 pearance and stiffness of leather and whichalso resembles leather in that it is non-fraying and can be skived likeleather.

The invention has as a further object the impregnation and processing ofunwoven textile fabrics or felts, and preferably a cotton felt, withcompositions containing rubber in such a manner that the resultingproduct has the characteristic properties of leather and particularlythe 45 stiffness and surface appearance of leather.

The objects of the invention are attained generally by treating thefabric felt, pad or matt from one side with rubber cement so as toimpregnate the material to aportion of its thick- 0 ness. The materialis then treated to impregnate the non-cemented portion with liquidlatex. The treatment with rubber cement decreases the tendency to shrinkwhen the latex is applied, reduces the quantity of latex required,serves as an 55 aid in imparting leather-like appearance to the product,and gives satisfactory stiffness and strength.

The invention will now be more fully described with reference to aspecific embodiment thereof, but it is to be understood that theinvention is not limited thereto.

A cotton felt '72 inches wide and weighing about 16 ounces to the yarddesignated as 16 ounce 72", is placed in roll lengths on an impregnatingmachine and is passed between two rolls which squeeze into one side ofthe felt a gasoline type curing cement of the following composition;

Pounds Ounces Pale crepe 19 0 20% sulphur master batch 2 0 Montan wax 40 Trimene base 8 Zinc oxide 5 0 Blanc fix 20 0 Albasan 4 The aboveingredients are dissolved in gasoline and thinned to the requiredviscosity so as'to regulate the depth of the impregnation, dependingupon thedesired stiffness and consolidation of the fibers required. Forgreater stiffness and deeper impregnation other viscosities may be used.The felt base is impregnated to about half its thickness, say about 0.02of an inch deep with about 4 oz. (dry weight) of cement per square yardand is then passed over suitable drying coils to remove the solvent fromthe cement. The roll of fabric thus partially impregnated from one sideis then placed on the same impregnating machine and impregnated from theopposite side stretching and would prevent the complete saturation ofthe fiber with latex which is accomplished in the time required forwinding and under the conditions of lack of tension which are present inthe wound piece. The impregnated material is then passed about three orfour times, over drying coils without tension to remove moisture and istl: en taken to a suitable consolidating machine, such as a calender ordoubling machine, and passed between squeeze rolls to consolidate it andto obtain a uniform gauge. The consolidated material is placed on asuitable rubber spreader and the face, or cement impregnated side isspread with a gasoline type curing cement similar to that referred toabove for impregnating purposes but containing suitable coloring matter,if desired. This spread coatds reduced to the proper thinness withgasoline and applied in such a manner that the fibrous appearance of theimpregnated material will be preserved, and not so dense or thick thatthe sur face will have the appearance of being smooth or composed ofrubber. Two spread coats, each of about 2 oz. (dry weight) of cement persquare yard of material, generally produce the desired appearance offibrous material and a suflicient amount of surface material so that thesurface can be readily embossed, but more or less can be used. Thecoated material is dried and embossed with a suitable grain to simulateleather and further to consolidate the fibers. The material is thenpassed through the curing chamber and vulcanized with heat for about 1hours at 250 F. although these conditions will vary somewhat inaccordance with the accelerator employed in the rubber.

' If a drier surface than that which is obtained by a dry heat cure isdesired, the embossed side may be treated with a solution of sulphurchloride or bromine and finally neutralized in the This manner wellknown in the art, such as by the application of ammonia vapor.

Many-modifications of the above embodiment of the invention may be made.Either a heatcuring or a cold-curing cement can be used. However, aheat-curing gasoline dispersed rubber cement is fully adequate for mostpurposes since it gives a drier, more leather-like surface and greaterstiffness. to the product. I desire to use a relatively highlyconcentrated dispersion of latex, such as that which is known under thetrade name Revertex and contains about 63 grams of solids per 100 c. 0.,but more or less concentrated aqueous latex dispersions can be used.Aqueous latex acts to consolidate, stiffen and toughen the material, andit gives the material greater resistance to fraying than do the organicsolvent-dispersed rubber compositions. More or less curing agent can beused in conjunction with the latex if more or less stiffness is desired,or for the more flexible products, no curing agent is incorporated. Thelatex dispersion may be used with or without fillers. A desirable waterdispersed composition which produces a distensible leather hav'ingexcellent properties contains latex with about 2.5 parts of zinc oxide,0.5 part of sulphur, 1.0 part of butyl zimate and 2.0 parts of 'coloringmatter in 100 parts. composition desirably contains small amounts of astabilizer such as caustic soda, a protective colloid such as caseinsolution, and a thickener such as gum tragacanth or starch.

Other methods than those enumerated in the example for thoroughly andcompletely impregnating the fibers with latex and drying with little orno tension may be used. A time element for saturation before drying andlack of tension are desirable. such as that which is obtained by windingthe materialxinto a roll as described but other means of obtaining theseoperating conditions can be used. For example, it would be sufrlcient ifsubstantially the same conditions were duplicated by the use of a tenterframe. The base material can be variously modifle from absorbent feltsor pads to absorbent woven. material or materials composed partly ofwoven and partly of unwoven material. Likewise many kinds of fibers canbe employed and other modifications can be made in the quantity ofimpregnating material and coating 'material used to suit the texture andfiber of'the base material and to modify the properties of the product.

Materials prepared in accordance with this invention closely resembleleather in stiffness and appearance and are therefore particularlyadapted for use as cuffs for gauntlets and as luggage materials. Theycan, however, also, be used for other purposes such as soling for shoesand quarter-lining materials.

Since many modifications of the invention may be made and some aresuggested by the foregoing description of the invention, it is to beunderstood that the invention is not limited to the particularembodiments herein described, and that no limitations are intended inthe claim except those which are specifically recited or imposed by theprior art.

I claim:

A process for the production of leather-like materials which comprisesimpregnating an absorbent sheet of felted textile fabric from but one ofits surfaces to a portion only of its thickness with a cement comprisinga solution of rubber in organic solvent of such viscosity to limit 4 itsimpregnation to a portion only of the thickness of the fabric, dryingthe cement, then impregnating from the un-impregnated surface theremaining portion of the sheet with rubber latex,

drying the impregnated fabric while maintaining

